Laundry detergent compositions need to have a very good fabric-cleaning performance against a wide variety of soil types. Solid laundry detergents also need to have very good dispensing and dissolution profiles. However, a dichotomy may exist in that some reformulations of the solid laundry detergent composition to improve its fabric-cleaning performance may negatively impact its dispensing and dissolution profiles, and vice versa. It is very difficult to improve the cleaning performance, dispensing profile and dissolution profile of a solid laundry detergent composition at the same time. Furthermore, it is also desirable for highly water-soluble solid laundry detergent compositions to form a clear wash liquor upon dissolution in water. This is because having a clear wash liquor is a desired consumer signal that the solid laundry detergent composition has dissolved.
Anionic detersive surfactants are incorporated into granular laundry detergent compositions in order to provide a good fabric-cleaning benefit. For example, GB1408969, GB1408970, U.S. Pat. No. 4,487,710, U.S. Pat. No. 5,663,136 and WO2004/041982 all relate to compositions comprising anionic detersive surfactants. However, the anionic detersive surfactant is capable of complexing with free cations, such as calcium and magnesium cations, that are present in the wash liquor in such a manner as to cause the anionic detersive surfactant to precipitate out of solution, which leads to a reduction in the anionic detersive surfactant activity. In extreme cases, these water-insoluble complexes may deposit onto the fabric resulting in poor whiteness maintenance and poor fabric integrity benefits. This is especially problematic when the laundry detergent composition is used in hard-water washing conditions when there is a high concentration of calcium cations.
The anionic detersive surfactant's tendency to complex with free cations in the wash liquor in such a manner as to precipitate out of solution is mitigated by the presence of builders, such as zeolite builders and phosphate builders, which have a high binding constant with cations such as calcium and magnesium cations. These builders sequester free calcium and magnesium cations and reduce the formation of these undesirable complexes. However, zeolite builders are water-insoluble and their incorporation in laundry detergent compositions leads to poor dissolution of the laundry detergent composition and can also lead to undesirable residues being deposited on the fabric. In addition, detergent compositions that comprise high levels of zeolite builder form undesirable cloudy wash liquors upon contact with water. Whilst phosphate builders allegedly do not have favourable environmental profiles and their use in laundry detergent compositions is becoming less common; for example, due to phosphate legislation in many countries.
Detergent compositions comprising alkyl benzene sulphonate and alkyl ethoxylated sulphate detersive surfactants are described in GB1408969, GB1408970, U.S. Pat. No. 4,487,710 and U.S. Pat. No. 5,663,136. A detergent composition comprising an anionic detersive surfactant and a non-ionic detersive surfactant that allegedly gives enhanced stain removal at a wide range of water-hardness is described in WO2004/041982.
There remains a need for a solid free flowing particulate laundry detergent composition comprising a detersive surfactant having a good fabric-cleaning performance, especially a good greasy stain cleaning performance, good whiteness maintenance, and very good dispensing and dissolution profiles, and which upon dissolution in water gives a clear wash liquor.